•DSC used to quantify semi-crystalline microplastics in environmental matrices.•Multiple heat-up steps significantly improve reliability and accuracy.•Microplastic mass concentrations can be measured ...fast and easily.
Microplastics can be quantified with the thermoanalytical method of differential scanning calorimetry (DSC). It is a standard method for quality testing in industrial production and processing of polymers. This study shows that DSC can be used for the quantification of semi-crystalline polymers in environmental matrices. A significant improvement of detection accuracy and limit was achieved with defined pre-heating and cooling steps. The pre-heating reduced the signals of organic impurities and harmonized polymer crystallinity in particles of different origins. This study introduces the method and presents limits of quantification for polyethylene (PE), polyethylene terephthalate (PET), polypropylene (PP) and polyamide6 (PA6) as well as accuracy in environmental samples, demonstrating the feasibility of this method for the first time.
Wastewater-based epidemiology (WBE) is a great approach that enables us to comprehensively monitor the community to determine the scale and dynamics of infections in a city, particularly in ...metropolitan cities with a high population density. Therefore, we monitored the time course of the SARS-CoV-2 RNA concentration in raw sewage in the Frankfurt metropolitan area, the European financial center. To determine the SARS-CoV-2 RNA concentration in sewage, we continuously collected 24 h composite samples twice a week from two wastewater treatment plant (WWTP) influents (Niederrad and Sindlingen) serving the Frankfurt metropolitan area and performed RT-qPCR analysis targeting three genes (N gene, S gene, and ORF1ab gene). In August, a resurgence in the SARS-CoV-2 RNA load was observed, reaching 3 × 10
copies/day, which represented similar levels compared to April with approx. 2 × 10
copies/day. This corresponds to a continuous increase again in COVID-19 cases in Frankfurt since August, with an average of 28.6 incidences, compared to 28.7 incidences in April. Different temporal dynamics were observed between different sampling points, indicating local dynamics in COVID-19 cases within the Frankfurt metropolitan area. The SARS-CoV-2 RNA load to the WWTP Niederrad ranged from approx. 4 × 10
to 1 × 10
copies/day, the load to the WWTP Sindlingen from approx. 1 × 10
to 2 × 10
copies/day, which resulted in a preceding increase in these loading in July ahead of the weekly averaged incidences. The study shows that WBE has the potential as an early warning system for SARS-CoV-2 infections and a monitoring system to identify global hotspots of COVID-19.
Partial Nitritation/Anammox (PN/A) is a well-established technology for side-stream nitrogen removal from highly concentrated, warm wastewaters. The focus has now shifted to weakly concentrated ...municipal wastewaters with much lower concentrations and temperatures. The major challenge is the temperature, which ranges from moderate 20 °C in summer to cold 10 °C in winter. For this study, the most frequently used configurations for side-stream applications were exposed to a slow temperature reduction from 20 °C to 10 °C to simulate a realistic temperature gradient. To evaluate the behavior of the different biomasses based on their properties, four lab reactors were operated in two different configurations. Synthetic wastewater was used to avoid side effects of heterotrophic growth. Differences in the response of the different reactor systems to this temperature gradient clearly indicated, that the geometry of the biomass has a major impact on the overall PN/A performance at low temperatures: While anammox activity in suspended biomass suffered already at 15 °C, it persevered in granular biomass as well as in biofilms on carriers for temperatures down to <13 °C. Further, anammox activity in thicker biofilms was less affected than in thinner biofilms and even adaption to low temperatures was observed.
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•Operation of 4 different PN/A reactors over a temperature gradient of 20° to 10 °C.•Thicker biofilms show better performance and less nitrite accumulation.•Biofilms (MBBR) retain more anammox biomass.•Microbial community in MBBR more stable than in SBR.
ABSTRACT Granular activated carbon (GAC) filtration is a commonly used method for advanced wastewater treatment. Filters can be operated continuously or discontinuously, with continuous operation not ...requiring feed flow interruption for backwashing and circulation (B/C). This study investigated the influence of B/C on the effluent quality of continuous filters. Two continuous GAC filters were operated for 1.5 years, with analysis of dissolved substances and particulate matter in the influent and effluent. The results indicated that various B/C modes had no impact on the removal of dissolved organic carbon and organic micropollutants (OMP), achieving an OMP removal of over 70% after 5,600 treated bed volumes (m3 treated wastewater per m3 GAC). However, it was evident that continuous B/C over 2–4 h resulted in increased turbidity, total suspended solids over 30 mg/L and total phosphorus concentrations of 1.3 mg/L in the filter effluent. Additionally, the study demonstrated that longer and more intensive B/C processes resulted in GAC size degradation with AC concentrations of up to 6.9 mg/L in the filter effluent, along with a change in GAC particle size. Furthermore, the importance of pre-filtration in reducing particulate matter in the filter influent and decreasing hydraulic head loss could be demonstrated.
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•Current design and operational strategies for mainstream PN/A are summarized.•Combined ON/OFF and IN/OUT strategies are necessary for successful operation.•A mechanistic framework ...linking engineering, microbiome, and modeling is proposed.•Knowledge readiness levels for key process indicators are defined.•Success relies on integrated research within the framework to boost predictability.
Twenty years ago, mainstream partial nitritation/anammox (PN/A) was conceptually proposed as pivotal for a more sustainable treatment of municipal wastewater. Its economic potential spurred research, yet practice awaits a comprehensive recipe for microbial resource management. Implementing mainstream PN/A requires transferable and operable ways to steer microbial competition as to meet discharge requirements on a year-round basis at satisfactory conversion rates. In essence, the competition for nitrogen, organic carbon and oxygen is grouped into ‘ON/OFF’ (suppression/promotion) and ‘IN/OUT’ (wash-out/retention and seeding) strategies, selecting for desirable conversions and microbes. Some insights need mechanistic understanding, while empirical observations suffice elsewhere. The provided methodological R&D framework integrates insights in engineering, microbiome and modeling. Such synergism should catalyze the implementation of energy-positive sewage treatment.
This study investigated the potential of Membrane-Aerated Biofilm Reactors (MABRs) for mainstream nitrogen removal via partial nitration/anaerobic ammonium oxidation (anammox). Four laboratory-scale ...MABRs were operated with real municipal wastewater characterized by low concentrations of nitrogen (varying between 31 and 120 mg–NH4–N L−1) and the presence of biodegradable organic carbon (soluble COD (sCOD) between 7 and 230 mg-O2 L−1). Two reactors were operated with different aeration strategies (intermittent vs. continuous), the other two with differences in biomass retention (recirculation or removal of detached biomass). Keeping a constant HRT caused instabilities due to difficulties with setting the optimal oxygen flux for the respective surface loadings (1.6–6 g–NH4–N m−2 d−1). Operating the MABRs with a constant surface loading (2 g–NH4–N m−2 d−1) resulted in higher and more stable total nitrogen (TN) removal independent of the aeration strategy. The intermittently aerated MABR improved from an average TN removal of 23%–69%, the continuously aerated MABR from 20% to 50% TN removal. Independent of the feeding strategy, the continuously aerated reactor removed slightly more ammonium (80–95%) compared to the intermittently aerated reactor (74–93%).
Limiting the oxygen supply by intermittent aeration proofed successful to favor partial nitritation and anammox. Continuous aeration did not achieve stable suppression of nitrite oxidizing bacteria (NOB). Of the removed ammonium, approx. 26% were left in the effluent as nitrate (only 10% with intermittent aeration).
Recirculation of the detached biomass resulted in reattachment onto the biofilm or membrane surface. This recirculation led to significantly higher biomass retention times and thus to better performance. Removing detached biofilm from the reactor caused a slightly lower TN removal of 33% compared to 45% with reattachment, while average ammonium removal was 58% compared to 63%, respectively. Scouring events had a significant impact on the overall operation, resulting in short term losses of TN removal capacities of 50–100%.
The microbial community composition was different depending on the aeration strategy and biomass retention. The continuously aerated reactor contained significantly more AOB than the intermittently aerated MABR. The reactor with biomass retention contained less ammonium oxidizing bacteria (AOB), compared to the reactor with low biomass retention. In all MABRs, anammox bacteria established in the biofilm after an initial drop in abundance.
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•MABRs show promising results for N-removal via PN/A under mainstream conditions.•Constant surface load resulted in a higher and more stable nitrogen removal.•Limiting the oxygen supply with intermittent aeration reduced nitrate production.•Consequent removal of detached biomass from the reactor caused a lower N-turnover.•All operational conditions allowed the establishment of AnAOB in the MABR biofilms.
Municipal wastewater collected in areas with moderate climate is subjected to a gradual temperature decrease from around 20 °C in summer to about 10 °C in winter. A lab-scale moving bed biofilm ...reactor (MBBR) with carrier material (K3 from AnoxKaldnes) was used to test the tolerance of the overall partial nitritation/anammox process to this temperature gradient. A synthetic influent, containing only ammonium and no organic carbon was used to minimize denitrification effects. After stable reactor operation at 20 °C, the temperature was slowly reduced by 2 °C per month and afterward held constant at 10 °C. Along the temperature decrease, the ammonium conversion dropped from an average of 40 gN m–3 d–1 (0.2 gN kgTSS h–1) at 20 °C to about 15 gN m–3 d–1 (0.07 gN kgTSS h–1) at 10 °C, while the effluent concentration was kept <8 mgNH4‑N l–1 during the whole operation. This also resulted in doubling of the hydraulic retention time over the temperature ramp. The MBBR with its biofilm on 10 mm thick carriers proved to sufficiently sustain enough biomass to allow anammox activity even at 10 °C. Even though there was a minor nitrite-build up when the temperature dropped below 12.5 °C, reactor performance recovered as the temperature decrease continued. Microbial community analysis by 16S rRNA amplicon analysis revealed a relatively stable community composition over the entire experimental period.
The Publisher regrets that this article is an accidental duplication of a published article, http://dx.doi.org/10.1016/j.wroa.2020.100066. The duplicate article has therefore been withdrawn. The ...full Elsevier Policy on Article Withdrawal can be found at https://www.elsevier.com/about/our-business/policies/article-withdrawal.The Publisher regrets that this article is an accidental duplication of a published article, http://dx.doi.org/10.1016/j.wroa.2020.100066. The duplicate article has therefore been withdrawn. The full Elsevier Policy on Article Withdrawal can be found at https://www.elsevier.com/about/our-business/policies/article-withdrawal.
A 1-d multi-population biofilm model was constructed to study the effect of heterotrophic activity on completely autotrophic ammonium (NH
4
+) removal in membrane-aerated (counter-diffusion) versus ...conventional biofilm systems (co-diffusion). Growth of heterotrophic bacteria (HB) was supported either solely by biomass decay products or by organic carbon (as chemical oxygen demand (COD)) in the influent. Three scenarios were considered: influence of HB growing on biomass decay products on steady-state performance (total nitrogen (TN) removal efficiency); influence of the influent COD/N ratio on steady-state performance (supplying COD in the influent); and impact of dynamic changes in the influent COD/N ratio on TN removal efficiency. The results revealed that the TN removal efficiency in the counter-diffusion biofilm was significantly different when HB were included in the simulations at NH
4
+ surface loads of
L
NH
4
>
2.7
g
-
N
m
-
2
d
-
1
. Influent COD significantly altered the microbial community composition in the counter-diffusion biofilm and anaerobic NH
4
+ oxidation could not be sustained at COD/N>2. The co-diffusion system, however, was less affected and more than 50% of the TN removal originated from anaerobic NH
4
+ oxidation at those ratios. Perturbation experiments showed that step increases to influent COD/N ratios of 2 or higher over a period of 50
d or longer caused a loss of anaerobic NH
4
+ oxidation capacity which could not be regained within a reasonable time frame (>1000
d) in the counter-diffusion system. In contrast, simulating a 1-d sloughing event only caused a disturbance of 200
d although a maximum biofilm loss of 90–95% occurred. These results clearly indicate the importance of heterotrophic activity in autotrophic N removal biofilms, especially in counter-diffusion systems where they may compromise N removal capacity.
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